The present invention relates generally to systems and methods for coordinated automatic formation turning for aircraft.
Some present Air Force aircraft (C-130 and C-141) incorporate AN/APN-169 Station Keeping Equipment (SKE) which is designed to enable pilots to maintain formation positions by providing them with raw position error data. Raw position error data are obtained by converting SKE radar range and bearing measurements into along heading and cross heading positions and comparing these to desired along heading and cross heading positions. SKE radar range and bearing measurements are obtained from a rotating antenna system approximately once each 1.5 seconds. The SKE equipment is designed primarily to accommodate relatively straight flights. During Air Force training flights in C-141 aircraft, it was noted that a problem exists with presently used manual systems for formation turns of more than about 6.degree. change of heading wherein substantial pilot workload was required to rapidly move throttles to extreme settings in the coordination of speed, heading, bank and time interval calculations during the turn. No systems exist in the prior art by which automatic formation turns may be satisfactorily effected. Specifically, prior art systems have ignored finite time and roll rates of the leader and follower during the roll-in and roll-out portions of the turns.
The present invention comprises a method for coordinated formation turning usable with the autopilot/autothrottle systems of large aircraft such as the C-17. The system provides pitch, roll, and throttle flight director signals which are provided directly to the autopilot system thereby providing a capability for completely automatic formation flight and for controlling formation turns of any degree. Position sensing (SKE) equipment aboard each aircraft in the formation provides data to the aircraft's computer of air speed, heading, etc. The computer in the follower aircraft then calculates in accordance with the invention, the acceleration and bank angle of each aircraft in formation, and the nominal range and bearing to the leader aircraft. Similarly the computer in the leader aircraft generates the bank angle for that aircraft.
The method of the present invention utilizes mission computers of the aircraft to automatic formation turns and provides relatively simple acceleration patterns for followers, maintains safe follower positions during a turn, and provides correct end-of-turn position, air speed and heading for each follower. Both long and short turns may be accommodated, and unbriefed turns may be performed without pre-announced end-of-turn heading. The longitudinal accelerations and decelerations required of follower wingmen are minimized by initiating follower acceleration and deceleration immediately upon leader roll-in and roll-out for long turns. The resulting longitudinal acceleration requirements are small, and permit formation turns over substantially all of the aircraft's normal operating flight envelope. Lateral positioning may be properly maintained even if a follower does not accelerate exactly as required. The workload of each pilot in formation is therefore substantially relieved.
It is, therefore, a principal object of the present invention to provide a method for automatic formation turns for aircraft.
It is a further object of the invention to provide a method for formation turns for aircraft wherein aircraft speed and formation position before and after a turn is accurately maintained.
These and other objects of the present invention will become apparent as the detailed description of certain representative embodiments thereof proceeds.